Да,равенство двух отношений-пропорция
1) (m:5+3)*6=46
(m/5 +3)*6=46
6m/5+18=46
6m+90=230
6m=230-90
6m=140
m=70/3
m=23 1/3 или m≈23,3
2)7*t-14=28
7t=28+14
7t=42
t=6
3)56:(36:r-2)=8
r≠18
r≠0
56:(36/r-2)=8
56:36-2r/r=8
56*r/36-2r=8
56*r/2(18-r)=8
28*r/2(18-r)=8
28*r/18-r=8
28r/18-r=8
28r=8(18-r)
28r=144-8r
28r+8r=144
36r=144
r=4
<span>(65+5)+9=79
</span>(76+4)+8=88
20+(7+3)+30=60
36+(8+2)=46
47+(6+4)=57
50+(9+1)+40=100
1) 14.5 - 30.1 = - (30.1 - 14.5) = - 15.6
2) 6.8 + 1.9 = 8.7
3) 23.6 + (-15.6) = 8
4) 8 - 8.7 = - 0.7
Ответ: - 0.7